Concentration and distillation of solutions of hydrogen peroxide



, able when working on a large scale, 5 troducing the dilute solution continuous y.

Patented Dec. 10, 1929 PATENT OFFHCE 16mm, or mnnnm, GERMANY,- axnnnensnrtscnnm, or rnnnxronr-on-rnnv OF GERMANY ASSIGNOBS TO G. FARBENINDUSTBIE GERMANY, A CORPORATION cononnrnarron AND msmm'rron or sonn'rrons or mnoenn' rnnoxmn m Drawing. Applicatiqn filed January is, 1927, Serial No. 161,956, and in Germany January 1a, 1926.

The production of highly concentratedv solutionsof hydrogen peroxide has hitherto been usually effected by means of the distilla tion in vvacuo, of the dilute solutions obtained I 5 by one of the ordinary methods. When workhowever, the catalytic influenceof impurities or the walls of the vessel employed for. the distillation readily lead to decomposition of the hydrogen peroxide, and

'ing in this manner,

this has fregliliently resulted in serious interru tions of e work, and even in explosions. It as been proposed in order to obviate these objections to concentrate the dilute solutions at ordinary pressure by fractional distillation i effected b passing a strong current'of gas through t e solutions at temperatures below 85 C. If, however, the last named process is applied to large quantities, a considerable proportion of the hydrogen peroxide also un- 20 dergoes decomposition, especially towards the end of the distillation. Moreover, it is impossible, to obtain concentrated hydrogen peroxide in a continuous manner as is desirb in- We have now found that a much im roved yield and acontinuousproduction of ighly concentrated hydrogen peroxide may be obtained by allowing the dilute solution contairing the hydrogen peroxide to flow in a finely divided state or m the form of a thin film or layer over substances presenting a large superficial area, or b atomizing it in chambers, and simultaneous y treating it with the assistanceof heat if necessary, with gases or vapors, preferably on the counterflow principle, so as to obtain intimate contactge c-.

v tween the solution and drying medium.

cording to this method of working it is possible to vaporize the bulk of the water without carrying away any appreciable quantity of the hydrogen peroxide, and as the solution is thus exposed to the action of the gases and heat. for only a short time, the hydrogen peroxide undergoes practically no decomposition. Y

The procedure to be adopted according to this invention may consist, for example, in

allowin the dilute solution to trickle, in a finely 1vided 'state, down in or flow along the walls of vertically or obliquely disposed pipes which are heated to 70 C. from outside whilst a current of preheated air, which has been dried for example by cooling or by the aid of adsorbents; ascends from below so as to meet the solution. The moisture laden air, issue'sfrom an upper lateral outlet from the p pes, andthe concentrated solution of peroxide drains away continuously from the I lower end, whereupon it is preferably cooled lmmediatel The processaccording to the present invention may be carried out in a still simpler manthe air supply. The external or internal heatartially or enmg f the columns may be tirely dispensed with, rovided the air or other drying medium to e used is preheated, a preferable way of effecting this being to utilize for this purpose the heat carried away in the current of moisture-laden exhaust gas.

, For the expulsion of the water, air may be reacting with the hydrogen peroxide solution and only to a small degree soluble therein. It

is preferable, however, to employ air, oxygen or other gases containing oxygen.v be exhaust gases may be returned to the circulation after their moisture content has been removed. It is frequently advisableto free the gases, prior to use, fromdust and other impurities which would cause decomposition of the hydrogen peroxide. Y

The present method can also be used with advantage for obtaining pure hydrogenperoxide solutions by the separation from mor-. anic constituents such as salts and the like y wavof distillation. As the vapor tension of hydrogen peroxide becomes the higher the replaced by any gases or vapors incapable of greater the concentration of the solution, the vapors of the liquid when applyin the above mentioned treatment will at lengt contain a considerable amount of. hydrogen peroxide vapor, and v by condensation of the mixture pure hydrogen peroxide solution is obtalned. When starting from a dilute impure hydrogen peroxide solution the-concentration of hydrogen peroxide in the distillate would be too low, and in such cases it is preferable to first concentrate the solution in the afore-described manner immediately before distillation. For this purpose for exampletwo trickling towers may be arranged either side by side or one on top of the other, the first of which servlng for concentrating the hydrogen peroxide solution by treating with a current of gas at a proper speed and temperature, whereupon in the second tower the concentrated h drogen peroxidesolution is distilled in a similar way but with a roperly altered speed and temperature. r still simpler, a single trickling tower is employed in the top of which the dilute impure solution is introduced while at the same time a strong current of hot airis introduced from below from which current .a portlon is branched ofl and carried away from the column at a spot where the hydrogen peroxide solution has been enriched to say 70 per cent when a condensate of about 20 per cent concentration of pure hydrogen peroxide is obtained. The remainder of the currentof air is passedfurther through the upper part of the column which it leaves at the top, and there practically only water vapor condenses in'correspondence with the vapor tension of the counter-flowing dilute solution. In the lower part of the column impurities are col- 1 'lected which being in the most cases, salts,

can give rise to clogging, and for avoiding this nuisance the lower part is not provided withfilling bodies, but a suitable device for example a worm conveyor may be arranged therein in order to withdraw the solid residues continuously.

The said process may also be modified by drawing off the water vapor by means of diminished pressure obtained by sucking off the wet gases and vapors more quickly than introducing, and passing through a current of gas. In this case, also, the operation may be rendered continuous b arranging the distillin plantso that the ibngth of the outlet pipe or the concentrated h drogen peroxide solution corres onds to the ii ence between tiie vacuum in the evaporation column and the external atmospheric pressure.

'The em loyment of diminished pressure may also e Combined with theabove described treatment with gases or vapors. Or

the treatment with gases or vapors may even be carried out under elevated pressure. We claim: 1. The process of producing concentrated our hands.

arometric difier:

pressure into intimate contact, with a gaseous dr ing medium.

eroxide which conn testimony whereof we have hereunto set OTTO KCHLER.

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